Hello Everyone ..Thanks for this conversation. :^)
-> 6mm airsoft is .... plastic BB's that will not break the skin. Meant to shoot * at * folks more than anything.
-> 4.5mm BB's are steel and are meant to shoot at pretty much anything * but * folks. They break the skin and can cause injuries! Cardboard boxes, foam targets, plastic soda bottles, aluminum cans drink etc make great targets.
-> You can not pick a "better" Between the Two Because they're Intended for Entirely different purposes. If you plan some serious target practice, the 4.5mm would probably be best .... but if you want airsoft fun with your friends, the 6mm is the way to go.